Weak and short La Nina fades away; climate shifts to neutral

U.S. weather forecasters said Thursday the cool flip side to the climate phenomenon El Nino has faded away.

The La Nina episode lasted only four months and was among the weakest and shortest on record, coming on the heels of one of the strongest El Ninos, said Mike Halpert of the National Oceanic and Atmospheric Administration's Climate Prediction Center.

La Nina, a cooling of parts of the equatorial Pacific that changes weather patterns worldwide, often lasts a year or more, longer than El Ninos. La Nina conditions were first detected in October and disappeared in January.

"Even though it was fairly weak and short-lived ... it did leave impacts," Halpert said, pointing to unusual cold in Alaska, western Canada and U.S. Northern Plains in December and January.

Strong La Ninas usually follow powerful El Ninos, which didn't happen in this case, said University of Washington atmospheric scientist Mike Wallace.

Many computer models show an El Nino forming later this summer or fall, but NOAA isn't making a prediction yet, Halpert said.

If an El Nino returns quickly, it would be fairly unusual. Switching from El Nino to La Nina and back in less than three years has happened only once before in the 1960s, Halpert said.

La Nina's disappearance leaves the world in what is called a neutral condition, making it tougher for meteorologists to make seasonal or long-term forecasts.

"In the forecast game you like big signals," Wallace said.

Because of persistent warming, forecasters will continue to call for warmer than normal temperatures for much of the United States.

"You can't really go wrong if you are forecasting above-normal temperatures for a large part of the country because that's what you get," Halpert said.